Mobile x-ray unit

ABSTRACT

One embodiment of the present disclosure is directed to a mobile X-ray unit. The mobile X-ray unit may include a base for accommodating a control unit for controlling an X-ray applicator and a power supply for supplying power to the X-ray applicator. The mobile X-ray unit may further include an articulated arm associated with the base and coupled to the X-ray applicator. The X-ray applicator may have an X-ray tube configured to emit an X-ray beam through an exit window to irradiate an object. The mobile X-ray unit may further include a dosimetry system adapted for real time dosimetry.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority based on U.S.Provisional Patent Application No. 61/426,917, filed Dec. 23, 2010, andNetherlands Patent Application No. 2005901, filed Dec. 22, 2010, whichare all incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates generally to a mobile X-ray unit. Thepresent disclosure further relates to a method for dosimetry controlusing an X-ray beam emitted from the mobile X-ray unit.

BACKGROUND OF THE INVENTION

The incidence rate of skin cancer has substantially increased in thelast decade of the 20^(th) century. It is appreciated that over 1.3million new skin cancers are diagnosed annually, which is increasing ata rate of about 5% per year. Increased exposure to the sun without skinprotection and a decreased ozone layer are regarded as the main causesof this increase—a problem estimated to be costing over 1 billion Eurosin annual medical treatment expenses. Over 80% of skin cancers occur inthe head and neck regions with 50% occurring in patients over 60 yearsof age. It is expected that a portion of the senior population willdouble in year 2025 compared to the present demographics. Because of thegrowing incidence of skin cancer and increasing share of the seniorpopulation in the overall demographics, much focus has been placed oncancer treatments and cancer treatment logistics.

Non-proliferative cancers, which are defined by substantiallysuperficial lesions, may be treated in different ways. In one example,non-proliferative cancers may be treated surgically. Surgery, may,however, have certain drawbacks, such as, for example, long waitinglists, complications related to post-treatment care, and risk ofinfection. Alternatively, patients may undergo irradiation usingelectrons of soft X-rays. Irradiation may have an advantage of beingnon-invasive and of a short duration (a treatment session may be asshort as 2 to 4 minutes). It will be appreciated that usually theintegral treatments using radiotherapeutic techniques may require anumber of sessions.

Recently, the use of a mobile and portable X-ray unit has beensuggested, which may be used inside a hospital radiotherapy department.An embodiment of such portable unit is described in US 2007/0076851.Existing X-ray units include an X-ray source and a filtering devicehaving a plurality of filters rotatably arranged with respect to a focalpoint of the X-ray tube for changing filtering characteristics ondemand. The plurality of filters are arranged in a filtering device,which is transversely arranged with respect to a longitudinal axis ofthe X-ray tube. In existing devices, the X-ray applicator is positionedat some distance from the patient's skin. Existing devices have certaindrawbacks. In one example, there may be poor control resulting indifficulty delineating between the X-ray beam emitted from the X-rayapplicator and a treated region on the patient.

SUMMARY OF THE INVENTION

It is an object of the disclosure to provide an improved mobile X-rayunit. In particular, it is an object of the disclosure to provide amobile X-ray unit having an X-ray beam delivered in a controlledfashion. To this end, the mobile X-ray unit, according to the presentdisclosure, may include a built-in dosimetry system adapted to carry outon-line or real-time dosimetry.

It will be appreciated that the terms ‘mobile’ and ‘portable’ in thecontext of the present application may be interchanged as these termsequally relate to an easily moved or transported device, for example, adevice which may be moved or transported by a single individual.

The dosimetry system may be built into the X-ray tube or the X-rayapplicator. Additionally and/or alternatively, the dosimetry system maybe configured between an exit window of the X-ray applicator and atarget region of an object (i.e., a patient) while being connected to acontrol unit of the mobile X-ray unit.

It may be advantageous to provide a dosimetry system which may beconfigured to deliver information substantially in real time, on theradiation dose distribution at or near the target region. The dosimetrysystem may include a film, a thermoluminescent device, or asemiconductor detector. However, it will be appreciated that other typesof commonly known dosimeters may be used as well. For example, asuitable ionization chamber may be used, having a parallel plateconfiguration, like a Markus chamber. These devices may be useful forcontrolling a profile of the X-ray beam.

When the dosimetry system is positioned inside the X-ray applicator orinside the X-ray tube, the dosimetry system may be positioned so as tobe outside a portion of the X-ray beam used for irradiating the patient.It will be appreciated that because the X-rays are generatedsubstantially in three-dimensions, such placing of the dosimetry systemis feasible.

In one embodiment, the dosimetry system may be calibrated based on theabsolute dose delivered by the X-ray tube. In this way, reliablereal-time dosimetry may be carried out.

It will be appreciated that it may be possible to either use a constantcalibration value for converting the detector read-out signal into adelivered dose, or, alternatively, to use a suitable equation,correcting for the lifetime of the detector, and/or for time to warm-upof the X-ray tube. In some embodiments, it may be possible to use acalibration factor which may be dependent on the position and/or angleof the X-ray applicator. This may be beneficial, as changes in thealignment of internal components of the X-ray applicator may cause adeviation of the delivered dose.

In some embodiments, the dosimetry system may be configured to transmita control signal to a control unit of the mobile X-ray unit after theX-ray tube has been switched on. In addition, the dosimeter system maybe configured to transmit a signal to the control unit of the mobileX-ray unit when a prescribed dose has been delivered.

In some embodiments, the dosimetry system may include a dose meter. Thedose meter may be positioned between the X-ray applicator and a targetregion of an object (i.e., patient). This arrangement may beadvantageous, as the dose meter may, by virtue of its material,establish an electronic equilibrium at or near the surface of theobject. As a result, the percentage depth dose build-up inside theobject may be determined relative to an absolute value of the surfacedose. It will be appreciated that for skin treatment the surface dosemay not be higher than 137% of the prescribed depth dose. Usually theprescribed depth dose is specified at a depth of 5 mm from the skinsurface.

Due to a presence of an additional material (a film or a detector) thepercentage depth dose inside the object may be changed to reduce thesurface dose when normalized with the dose at 5 mm depth.

In various embodiments, the dosimetry system may include a digitalreadout device. It may be advantageous to enable real-time dataacquisition and data processing by using a digital dosimeter, which maybe connected to the control unit of the mobile X-ray unit so as tofacilitate a substantially direct hardware response should the measureddose substantially deviate from the prescribed dose. It will beappreciated, that a film may be used for dosimetry purposes which may besubsequently read-out using a digital densitometer.

It will be appreciated that the dosimetry system may be arranged toelectronically communicate with the control unit. In particular, thedosimetry system may have either an analogue or a digital signal as anoutput. Those skilled in the art will readily appreciate whichelectronic devices (if any) may be necessary for enabling datacommunication between the dosimetry system and the control unit of themobile X-ray unit.

In various embodiments, the dosimetry system may be configured enableverification of at least a position and geometry of a generated X-rayfield.

The dosimetry system, i.e. a film or a device (thermoluminiscent,ionization chamber or a semiconductor), may include a plurality ofmeasuring points, preferably distributed in a plane. When the dosimetrysystem is positioned in the X-ray field, the readings may be processedfor establishing dose data across the applied field. For example, areading at the central axis may be obtained, and a number of peripheralreadings, preferably at different radial distances, may be obtained. Asa result, information may be obtained regarding not only the absolutedose in the central field, but also information about beam flatnessacross the field. In some embodiments, the dosimetry unit may becalibrated to calculate an absolute dosimetry of an X-ray dose. Suchcalibration may be carried out by, for example, using a trialmeasurement for a known X-ray dose.

In various embodiments, the X-ray applicator may include an indicatorfor visualizing at least a portion of the X-ray beam emitting from theexit surface of the applicator.

Treatment efficacy may be substantially improved when an indicator isprovided for delineating at least a portion of the generated X-ray beam,like a central axis thereof, and/or a partial or a full beam geometry.In particular, an indicator may be advantageous for positioning thedosimetry system with respect to the X-ray beam. In an exemplaryembodiment, the indicator is a light source. The light source may bearranged in the X-ray applicator or, alternatively, the light source maybe arranged around an outer surface of the X-ray applicator. When thelight source is arranged in the X-ray applicator, the light source maybe configured to delineate the central axis of the X-ray beam and/or thefull beam geometry. When the light source is arranged around the outersurface of the X-ray applicator, the light source may be arranged todelineate a central axis of the X-ray beam, preferably at apre-determined distance from the X-ray applicator. This may beadvantageous when the X-ray applicator is used at a standard distancefrom the patient's skin. However, it will be appreciated that the lightsource arranged around the X-ray applicator may be adjusted so as toindicate the central axis of the X-ray beam at a variety of axialdistances from the X-ray applicator.

In various embodiments, the indicator includes an array of light sourcesconcentrically arranged around the X-ray applicator. Although it may besufficient to provide a single light source that generates a narrow beamfor indicating the central axis of the X-ray beam, it may beadvantageous to provide a plurality of light sources each of whichgenerates a narrow light beam. These light beams may intersect at agiven distance from the lower surface of the X-ray applicator. In thismanner, the X-ray applicator may be positioned at a prescribed distancefrom the skin. Additionally, the dosimetry system may be positioned withrespect to the X-ray beam. In order to ensure a correct coverage of thetarget region by the X-ray beam, the X-ray applicator may be positionedso that the indicated center of the X-ray beam is positionedsubstantially at a center of the target region. It will be appreciatedthat these embodiments function particularly well for regular shapedX-ray beams, for example, when a circular, a square, an elliptic, or atriangular collimator is used for shaping the X-ray beam.

In various embodiments, the light source may be disposed inside theX-ray applicator for generating a light beam configured to beintercepted by a collimator for providing a light image of the X-rayfield emitted from the exit window.

This embodiment may be advantageous when the full shape of the X-raybeam is to be delineated such as, for example, in situations when anirregular beam shape is used. In such cases, the light source may beprovided near the target region or, via a mirror, off-axis, forgenerating a light beam configured to be intercepted by the collimator.It will be appreciated that a direction of propagation of the light beammust essentially conform to a direction of propagation of the X-raybeam. In one embodiment, when a mirror is used, the light source mayadvantageously be positioned off-axis minimizing its radiation damage.

In various embodiments, the indicator includes a light source and anoptical fiber configured to deliver light from the light source forinterception by the collimator.

This may be advantageous as the light source may be positioned outsidethe X-ray applicator in order maintain the overall size of the X-rayapplicator. For example, the light source may be arranged in the base ofthe X-ray unit and the optical fibers may run from the base to insidethe X-ray applicator for suitably illuminating the collimator forobtaining a light image equivalent to that of the generated X-ray beam.

In various embodiments of the present disclosure, the indicator mayinclude a plurality of optical fibers distributed in the X-rayapplicator in an area above the collimator for illuminating a collimatoropening for causing the collimator opening to intercept the resultinglight field. This embodiment may be advantageous for obtaining a lightfield having substantial intensity.

In various embodiments, the indicator may include a light sourceemitting a narrow light beam arranged inside the applicator fordelineating a longitudinal axis of the X-ray beam. Preferably, aminiature laser source may be used.

In a still further embodiment of the X-ray unit according to theinvention a radiation detector may be provided inside the outer housingfor detecting the X-ray beam.

It may be advantageous to provide an independent mechanism for detectingthe presence of an X-ray beam. In some embodiments, the X-ray unitincludes a primary timer which may set a time for the high voltagesupply to deliver a predetermined radiation dose. The radiation sensordisposed inside the outer housing of the X-ray applicator may be part ofa secondary timer circuit adapted to shut down the high voltage supplywhen the predetermined radiation dose has been delivered. In this wayradiation safety control may be improved.

In some embodiments, in which a dosimetry system may provide data inreal-time, the signal from the dosimetry system may be used in additionto the signal from the built in radiation detector. In particular, whenthe dosimetry system is arranged to verify the beam characteristic, asubstantial deviation from the prescribed beam flatness may be used as acontrol signal to shut-down the mobile X-ray unit.

In some embodiments, the X-ray applicator includes an exit surfaceconfigured to be oriented towards a patient, the surface may be coveredby an applicator cap.

It may be advantageous to provide an applicator cap, which may have manyfunctions in use. In one example, the applicator cap may be used forprotecting the exit surface of the X-ray applicator from intra-patientcontamination. In another example, the thickness of the cap in adirection of the beam propagation may be sufficient for substantiallyeliminating electron contamination from the X-ray beam. In someembodiments, the applicator cap may be manufactured from PVDF(Polyvinylidene fluoride) and may have a thickness of about 0.4-0.7 mm,preferably 0.6 mm, across the window portion. The applicator cap mayhave a density of about 1.75-1.8, and preferably 1.78. In otherembodiments, the applicator cap may have a thickness of 0.3-0.6 mm, andpreferably 0.5 mm, across the window portion. In these embodiments, theapplicator cap may have a density of 1.30-1.45, and preferably 1.39, andmay be manufactured from PPSU (polyphenylsulfone). It is found thatthese materials may be particularly suitable as they are stable underinfluence of the X-rays and are suitable for different types ofsterilization procedures, such as chemical sterilization, orsterilization under elevated temperatures. It will be appreciated thatthose skilled in the art will readily appreciate the relationshipbetween the energy of the secondary electrons emanating from the X-raytube and a required thickness of a given material, such as, for exampleplastic, glass, ceramics, sufficient for fully intercepting theseelectrons. In some embodiments, the applicator cap may be disposable.

It will be appreciated that the indicator configured to delineate theX-ray beam may be configured to have sufficient intensity to provide afield image through the applicator cap. Lasers may be particularlysuited for this purpose. Alternatively, light emitting diodes may beused. In another embodiment, an arrangement of one or more light sourcesgenerating a narrow beam outside the X-ray applicator may beadvantageous. In that embodiment, one or more sources may be arranged onrespective support arm such that the respective narrow light beams arenot intercepted by the applicator cap.

Another embodiment of the present disclosure is related to a method fordosimetry control of an X-ray beam emitted from a mobile X-ray unit. Themobile X-ray unit may include a base for accommodating a control unitand a power supply. The mobile X-ray unit may further include anarticulated arm associated with the base. The articulated arm may beconfigured to support an X-ray applicator having an X-ray tube forgenerating an X-ray beam. The method may include measuring a parameterassociated with the X-ray beam using a built-in dosimetry system. Themethod may further include measuring the parameter in real-time.

In various embodiments, an indicator may be provided in or near theX-ray applicator for visually delineating at least a portion of theX-ray beam, which may assist in positioning the dosimetry system. Insome embodiments, the indicator includes a light source arranged togenerate a light field that may be intercepted by a collimator openingfor providing visualization of the X-ray beam. In another embodiment,the indicator may include a light source arranged to delineate alongitudinal axis of the X-ray beam.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one (several) embodiment(s) ofthe invention and together with the description, serve to explain theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a presents a perspective view of a mobile X-ray unit, accordingto embodiments of the present disclosure.

FIG. 1 b presents a partial perspective view of a mobile X-ray unitillustrating movement of a displaceable panel, according to embodimentsof the present disclosure.

FIG. 1 c presents a schematic view of the mobile X-ray unit shown inFIGS. 1 a and 1 b, illustrating displacement of an X-ray applicator ofthe X-ray unit relative to a base of the mobile X-ray unit, according toembodiments of the present disclosure.

FIG. 2 presents a diagrammatic representation of the mobile X-ray unit,according to embodiments of the present disclosure.

FIG. 3 presents a schematic view of a dosimetry system of the X-ray unitaccording to the invention.

FIG. 4 a presents a cross-sectional view of an X-ray applicator of themobile X-ray unit having an indicator, according to a first embodimentof the present disclosure.

FIG. 4 b presents a cross-sectional view of an X-ray applicator of themobile X-ray unit having an indicator, according to a second embodimentof the present disclosure.

FIG. 4 c presents a cross-sectional view of an X-ray applicator of themobile X-ray unit having an indicator, according to a third embodimentof the present disclosure.

FIG. 5 presents a partial perspective view of the X-ray applicatorprovided with an applicator cap, according to embodiments of the presentdisclosure.

FIG. 6 presents an end view of the X-ray tube, according to embodimentsof the present disclosure.

FIG. 6, E-E presents a cross-section along line VII-E of the X-ray tubeof FIG. 6, according to embodiments of the present disclosure.

FIG. 6, F-F presents a cross-section along line VII-F of the X-ray tubeof FIG. 6, according to embodiments of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present exemplaryembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

FIG. 1 a presents a partial perspective view of a mobile X-ray unitaccording to the present disclosure. The mobile X-ray unit 10 includes abase 2 having at least a high voltage supply unit, a cooling system, anda control unit (FIG. 2) for controlling operation of an X-ray applicator4. The X-ray applicator 4 includes an X-ray tube (FIG. 3) disposed in anouter housing of the X-ray applicator 4. The X-ray applicator 4 may beconnected to the base 2 using flexible cables 3, which may be at leastpartially disposed in a displaceable panel 5. The X-ray applicator 4 maybe coupled to an articulated arm 4 a, which may include a pivot forvarying the position of the X-ray applicator 4 in space. The X-rayapplicator 4 may include a longitudinal axis and an exit window 8through which the generated X-ray beam 8 a may be emitted. Thearticulated arm 4 a may also be connected to the displaceable panel 5 tochange a vertical position of the applicator 4. In some embodiments, thedisplaceable panel 5 may be provided with a handle 6 enabling easymanipulation thereof. The displaceable panel 5 may be guided alongsuitable rails for enabling a substantially smooth and shock-freedisplacement thereof.

In one embodiment, the X-ray applicator and the X-ray tube may becoaxially disposed. A longitudinal axis of an anode of the X-rayapplicator may be substantially parallel to a longitudinal axis of theX-ray applicator so that the X-ray beam 8 a may propagate from the exitwindow 8 having a beam axis 8 b substantially corresponding to alongitudinal axis of the X-ray tube.

In various embodiments, a dosimetry system 9 may be provided to providedata on at least a portion of the X-ray field 8 a at or near the surfaceP′ of the patient P. The dosimetry system may include ionizationchambers, solid state detectors, and semiconductor detectors. In oneembodiment, the system may be capable of generating real-time. In someembodiments, the signal from the dosimetry system may be supplied intothe control unit 21 of the mobile X-ray unit for real-time dose deliverycontrol.

In some embodiments, an indicator may be provided to position the X-rayapplicator 4 and the dosimetry system 9 with respect to a target regionon the surface P′ of a patient P. The indicator may be used to delineatethe X-ray field generated by the X-ray tube (FIG. 3) inside the X-rayapplicator 4. In some embodiment, the indicator may be a light source,such as, for example, a light emitting diode, a laser, or the like.

The light source may be arranged either inside the X-ray applicator 4,or around the X-ray applicator 4, or it may be remotely positioned, forexample in the base 2. In the latter case, light from the light from thelight source (not shown) may be conducted towards the X-ray applicatorusing one or more optical fibers. More details on suitable light sourcearrangements, although not limitative, are discussed with reference toFIGS. 4 a-4 c.

The displaceable panel 5 may include a display 7, which may function asa suitable user interface 7 a. For example, the patient data, such as aphoto of the patient and/or a photo of a lesion may be provided inwindow 7 b, whereby relevant patient information, such as the date ofbirth, gender, dose prescription, and dose delivery protocol may bedisplayed in window 7 c. Buttons 7 d may be provided as touchfunctionality for enabling entering data. Additionally and/oralternatively, suitable hardware switches or buttons may be provided aswell.

In some embodiments, the display 7 may be arranged as a touch-sensitivescreen for enabling suitable data input into the system. For example,the display panel may comprise buttons or switches for switching theindicator (i.e., light source) on. Optionally, the indicator may alwaysbe on when the X-ray unit is switched on. The user interface may furtherbe used to input a prescribed dose and, possibly, a prescribed dosedistribution, especially when dose modifiers are used for providing agradient in the dose profile across the X-ray field. The user interfacemay also be arranged to display data on actual dose delivery and dosedistribution profile during the treatment. It will be appreciated thatby using the dosimetry system the dose delivery protocol may be comparedwith actual dose delivery data in real time and, if necessary, theactual dose delivery may be corrected in real time and/or during furthersessions should a discrepancy in prescribed and delivered dose of morethan 1% occur.

FIG. 1 b presents a partial perspective view of the mobile X-ray unitillustrating movement of the displaceable panel. In this enlarged view10 a, specific elements of the displaceable panel 5 are depicted. Ahandle 6 may be implemented as a mechanical item for pulling or pushingthe displaceable panel 5. Alternatively, the handle 6 may be arranged asan electrical actuator for triggering motors (not shown) for displacingthe displaceable panel 5. For example, when the handle 6 is pulled themotors may be activated for causing the panel 5 to displace in adirection A. Pushing of the handle 6 may cause lowering of the panel 5in a direction B. In some embodiments, the mobile X-ray unit 10 includesstops, limits, or other known structures for limiting the movement ofthe displaceable panel 5. This may be advantageous for ensuringmechanical stability of the mobile X-ray unit 10 (limitation of theupper level) and may also be beneficial for preventing cable damage(limitation of the lower level). In some embodiments, the displaceablepanel 5 may travel along built-in rails whose length may be chosen forlimiting the displacement range of the panel 5 in a desirable way.

FIG. 1 c illustrates the displacement of the X-ray applicator 4 of theX-ray unit 10. It will be understood that the mobile X-ray unit 10 maybe configured so as to support a broad range of translational androtational movements of the X-ray applicator 4.

In view 11, the X-ray applicator 4 is in a retracted position. It willbe appreciated that cabling is not depicted for clarity reasons. Theretracted position may be suitable for transport of the mobile X-rayunit 10 towards a booth and/or for maneuvering the X-ray unit 10 aroundthe patient. In order to retract the X-ray applicator 4 as close aspossible to the base 2, the articulated arm 4 a may be positioned underthe outer portion 5 a of the displaceable panel 5. For ensuringstability of the mobile X-ray unit 10 during maneuvering thereof, a loadblock 2 a may be provided for lowering the point of gravity of the X-rayunit 10.

In view 12, the X-ray applicator 4 may be in an extended position (i.e.,working position) having an X-ray exit surface 8 oriented towards apatient P. In order to suitably position the X-ray applicator 4 withrespect to the patient P, the displaceable panel 5 may be moved to anintermediate position located between a lowest stand position and ahighest stand position of the displaceable panel 5. The articulated arm4 a may be used for suitably rotating the X-ray applicator 4 about arotation axis. In one embodiment, a rotation axis is selected tocoincide with a direction include the X-ray beam is emitted from an exitwindow 8 for a vertically oriented X-ray applicator 4.

In view 13, the X-ray applicator 4 may be in a lowered position. Forthis purpose the displaceable panel 5 may be in its lowest position andthe arm 4 a may be used for orienting the X-ray applicator 4 in adesirable way.

FIG. 2 is a diagrammatic representation of the mobile X-ray unit 10according to embodiments of the disclosure. The mobile X-ray unit 10includes a high voltage supply, preferably adapted to generate 50-75 kVX-rays in a suitable X-ray tube, a cooling system 21 d for cooling theX-ray tube during use, and a control system 21 for controllingelectronic and electric parameters of sub-units of the X-ray unit duringuse. View 20 diagrammatically depicts main units of the control system21 and of the X-ray applicator 22.

The control system 21 may include a hard wired user interface 21 a forenabling a user to switch on and switch off of the high voltage supply21 b. In some embodiments, the high voltage supply 21 b includes a highvoltage generator 21 c with improved ramp-up and ramp-downcharacteristics. The high voltage supply may be operable to deliverpower of about 200 W in use. In some embodiments, the ramp-up time maybe of the order of 100 ms. The hard wired interface 21 a, may also bearranged to automatically switch on the cooling system 21 d when thehigh voltage generator 21 c is switched on. In addition, the controlsystem 21 may include a primary controller 21 e arranged for controllingthe dose delivery from the X-ray applicator 22. The primary controller21 e may be provided with a primary counter adapted to register timelapsed after the X-ray radiation is initiated. The primary counter maythen automatically switch off the high voltage supply 21 b to the X-raytube 22 a in the event a pre-determined dose is reached. It will beappreciated that the pre-determined dose is at least dependent on theenergy of the X-rays and the dose rate, which may be calibrated inadvance. Where calibrated data is made available to the primarycontroller 21 e, adequate primary dose delivery control may be achieved.In some embodiments, a secondary controller 21 f may be provided forenabling an independent loop of dose delivery control. The secondarycontroller 21 f may be connected to a dose meter accommodated inside theX-ray applicator 22 in the X-ray field before the collimator 22 d.Accordingly, the dose meter may provide real-time data on actual dosedelivery taking into account dose variation during ramp up and ramp downof the high voltage source. Still preferably, the control system 21 mayinclude a safety controller 21 g adapted to compare readings from theprimary controller 21 e and the secondary controller 21 g for switchingoff the high voltage generator 21 c after a desired dose is delivered.Additionally and/or alternatively, the safety controller 21 g may bewired to guard emergency stop, door interlock, and a generatorinterlock.

The control system 21 may further include a dosimetry control 21 h,configured to communicate with a dosimetry system on-line. It is alsopossible that the dosimetry control 21 h may accept data from a scanneddosimetric field and update dose delivery data post-processing.

The dosimetry control 21 h may be arranged to provide an interruptsignal, should the real-time dosimeter measure a substantial deviationbetween the prescribed dose and the measured dose. For example, thedosimetry control 21 h may provide a suitable interrupt signal to thehigh voltage generator control 21 c to switch off the high voltagegenerator 21 c.

The control system 21 may further include an indicator controller 21 ifor controlling an indicator (i.e., a light source) used to delineate atleast a portion of the X-ray beam. In some embodiments, the indicatorcontroller 21 i may be linked to a power supply unit 21 b for switchingon the light source once the system is on. Alternatively, the lightsource may be switched on demand. Accordingly, the indicator controller21 i may be arranged to provide electrical power to the light sourcewhen triggered by the user. The user may provide a suitable triggersignal by a user interface, or, for example, using a dedicated hardwareswitch.

The X-ray applicator 22 may include an X-ray tube 22 a housed in anouter housing (shielding) 22 k. In the exemplary embodiment, a target, acollimator 22 d, and an exit window (FIG. 1 a) of the X-ray applicator22 may be in parallel so that the generated X-ray beam may be propagatedsubstantially parallel to a longitudinal axis of the X-ray tube 22 a.The X-ray tube 22 a may have a target-collimator distance of between 4and 10 cm, and preferably 5 and 6 cm. The X-ray applicator 22 mayfurther include a beam hardening filter 22 b selected to interceptlow-energy radiation and a beam flattening filter 22 c, designed tointercept portions of X-ray radiation for generating a substantiallyflat beam profile near the exit surface of the X-ray applicator 22.Further, the X-ray applicator 22 may include one or more collimators 22d arranged to define the shape of the X-ray beam. In some embodiments, aset of collimators 22 d may be used having, for example, diameters of 1,1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5 cm. It will be appreciated thatalthough circular collimators are discussed, collimators of any shape,such as square, elliptic or custom made collimators are possible. It maybe advantageous to have an X-ray applicator 22 with automatic collimatordetection device 22 f configured to automatically signal whichcollimator is being used. In some embodiments, resistive sensing may beused to identify which collimater 22 d is being used. In particular,each collimator may be provided with at least a couple of projectionsfor bridging a resistive path provided in a collimator receptacle (FIG.5). The resulting electrical resistance of the receptacle constitutes asignal representative of a collimator being used.

The X-ray applicator 22 may also include a built-in temperature sensor22 g adapted to monitor a temperature of the X-ray tube 22 a and/or itsshielding 22 k. The signal from the temperature sensor 22 g may bereceived by the control system 21 which may carry out the analysisthereof. Should the measured temperature be elevated beyond an allowablelevel, an alarm signal may be generated. Optionally, a shut-off signalto the high voltage generator may be provided. The X-ray applicator 22may further include a radiation sensor 22 h arranged inside the outerhousing 22 k for detecting X-ray radiation which may be delivered by theX-ray tube 22 a. Preferably, for safety reasons the X-ray applicator 22may include a non-volatile data storage 22 i arranged for recordingoperational parameters of at least the X-ray tube 22 a. Further, toenhance radiation safety, the X-ray applicator 22 may be provided with aradiation indicator 22 j arranged for providing a visual and/or an audiooutput to the user and/or the patient regarding ON/OFF condition of theX-ray tube 22 a. It will be appreciated that the radiation indicator 22j may include a plurality of signaling devices. In one embodiment, atleast one signaling device, for example a light emitting diode (LED),may be associated with the X-ray applicator 22 and provided on the X-rayapplicator 22. It is understood, however, that the signaling devices maybe positioned at any other location on the mobile X-ray unit.

FIG. 3 presents a schematic view of a dosimetry system of the X-rayunit. The X-ray applicator 4 discussed above may include an X-ray tubearranged with an anode 1 having a target 1 a for generating a divergingX-ray beam 8 a. The target 1 a may be a substantially flat plate whichmay extend substantially perpendicular to a longitudinal axis of theanode 1. In one embodiment, the anode 1 may be aligned along axis 8 b ofthe X-ray beam (and the X-ray tube), however, it is understood thatother respective orientations are possible. The X-ray beam 8 b may beemitted from an exit surface 8′ of the X-ray applicator. It will beappreciated that suitable filters, a collimator, and an exit window ofthe X-ray tube are not depicted for clarity reasons. Accordingly, theexit surface 8′ does not necessarily correspond to the exit window ofthe X-ray tube.

In one embodiment, an indicator such as, for example, a light source,may be used to position the X-ray applicator 4 with respect to a targetregion on an object (i.e., patient). In one embodiment, the indicatormay include two light sources 15 a, 15 b configured to generate a narrowbeam light. In this embodiment, the light sources 15 a, 15 b may bemounted on respective support arms 16 a, 16 b on an outer surface of theX-ray applicator 4. Preferably, the light sources 15 a, 15 b may beconfigured to provide a point in space C corresponding to the beam axis8 b. A dosimetry system may include a dosimetric device 18 that may thenbe centralized with respect to the point C for intercepting the X-raybeam.

In some embodiments, the mobile X-ray unit may be provided with aplurality of dosimetric devices of different size. A suitable dosimetricdevice 18 may be selected based on the actual beam size. In someembodiments, the dosimetric device 18 may extend further than the X-rayfield for measuring an absolute dimension of the X-ray field.

In some embodiments, the dosimetric device 18 may include an array ofindependent measuring volumes. It will be appreciated that for thispurpose a film may be used, a set of TLD devices, or an array-typesemiconductor dosimeter. As a result, dose distribution across the X-rayfield may be established for verification and/or for intra-fractioncorrection.

In some embodiments, the dosimetric device 18 may provide data in realtime. In particular, the dosimetric device may be connected to adosimetric control unit 21 h, as discussed with reference to FIG. 2.

Although an embodiment of the dosimetric system is discussed withreference to the X-ray applicator provided with an indicator (i.e.,light source), it will be appreciated that dosimetric system may beutilized without an indicator to delineate the X-ray field.

FIG. 4 a presents a cross-section of an X-ray applicator of the mobileX-ray unit having an indicator, in accordance with a first embodiment ofthe present disclosure. The X-ray applicator 30 includes an outerhousing 36 and an X-ray tube 35 disposed in the outer housing 36. TheX-ray tube 35 may have an external shielding 35 a, a target (not shown),and a collimator 33.

In one embodiment, the indicator may be light source 48 a. The lightsource 48 may cooperating with a mirror 48 for emitting a light beamindicative of a two-dimensional beam of X-rays produced by the X-raytube 35. In some embodiments, X-rays have a propagation axis 45 a whichcoincides with a longitudinal axis of the X-ray tube 35. The lightsource 48 a and the mirror 48 may be arranged so that the light beam maysubstantially propagate along the longitudinal axis of the X-ray tube 45a.

When the light beam is intercepted by a collimator 33 a visualindication and simulation of the two-dimensional X-ray beam is created.In one embodiment, the distance between a target of the anode (notshown) and the collimator 33 is in the range of 4 to 10 cm, preferablyabout 5 to 6 cm. Such relatively short target-collimator distance maygenerate an X-ray beam having a substantially narrow penumbra (1.5-1.8mm for 20/80% lines) and good beam flatness due to a relatively smallfocal size.

The X-ray applicator 30 may further include a filter 39 for hardeningthe X-ray beam generated at the target, a beam flattening filter 40 forflattening out a beam profile, and a collimator receptacle 41 forreceiving collimator 33.

A cooling system 34 may be provided so as to prevent overheating of theX-ray tube 35. In one embodiment, the cooling system 34 may be arrangedin the space between the X-ray tube 35 and the shielding 35 a in contactwith the surface of the X-ray tube 35. A suitable coolant may beprovided using a pipe 31. It is contemplated that the coolant may bewater, a pressurized gas, or even a special oil. The X-ray applicator 30may further include a temperature sensor 37.

The X-ray assembly 30 may further include a suitable radiation detector38 connected to a radiation indicator 43. Data collected by theradiation detector 38 may be stored in a data storage unit 44.

In order to protect the X-ray exit surface (including window) of theX-ray applicator 30 from intra-patient contamination, an applicator cap42 may be provided to cover at least the exit surface of the X-rayapplicator 30. In some embodiments, the applicator cap 42 is thickenough to fully intercept secondary electrons emanating from the X-rayapplicator 30. The applicator cap 32 may be manufactured from PVDF(polyvinylidene fluoride) and may be about 0.4-0.7 mm, and preferably0.6 mm thick across the window portion. The applicator cap may havedensity of about 1.75-1.8, and preferably 1.78. Alternatively theapplicator cap 42 may be 0.3-0.6 mm thick, and preferably 0.5 mm thickacross the window portion. In those embodiments, the applicator cap 32may have a density of 1.30-1.45, and preferably 1.39. Further, theapplicator cap 42 may be manufactured from PPSU (polyphenylsulfone).These materials may be particularly suitable as they as stable underinfluence of the X-rays and are suitable for different types ofsterilization procedures, such as chemical sterilization, orsterilization under elevated temperatures.

FIG. 4 b presents a cross-section of an X-ray applicator of the mobileX-ray unit having an indicator, in accordance with a second embodimentof the present disclosure. In this exemplary embodiment, the indicatorincludes at least one optical fiber 47 a connected to a light sourcethat may be positioned remotely in, for example, base 2.

Optical fiber 47 a may be provided in the collimator receptacle 41 abovethe collimator 33. The optical fiber 47 a may be configured to generatea light field that is substantially centered about the collimatoropening 33 for creating a two-dimensional cross-section of an X-ray beamemitted from the collimator 33. In this embodiment, optical fiber 47 amay be configured to emit a substantially narrow beam having adivergence of the expected divergence of the X-ray beam.

Alternatively, it may be possible to use the optical fiber 47 a forvisualizing a central axis 45 a of the X-ray beam in addition tovisualizing the two-dimensional area of the X-ray beam. In this case,the optical fiber may be arranged to emit a narrow beam light producinga miniature light spot on a surface of the patient. In one embodiment, adimension of the light spot is less than 5 mm², and more preferably adimension of the light spot is about 1 mm². A suitable light emittingdiode or a laser may be used for generating light emitted from the fiber47 a. In one embodiment, the light emitting diode and the laser areremotely arranged with respect to the X-ray applicator 30. It will beappreciated that an alternative configuration may be used such as forexample, having one or more light sources that may be electricallyconnected to one or more optical fibers.

FIG. 4 c presents a cross-section of an X-ray applicator 30 of themobile X-ray unit having an indicator in accordance with a thirdembodiment of the present disclosure. In this exemplary embodiment, theindicator may be disposed externally of the X-ray applicator 30 and maybe one or more light sources 52.

As illustrated in FIG. 4 c, the X-ray applicator 30 may include an anode45 provided with a target for generating an X-ray beam 45 c having alongitudinal X-ray axis 45 a. The one or more light source 52 may beconfigured to illuminate the longitudinal axis 45 a of the X-ray beam 45c at a pre-determined distance D from the lower surface 49 of the X-rayapplicator 30. It will be appreciated that the lower surface 49 mayrelate to the exit window as discussed with reference to FIG. 1 c, or itmay relate to the applicator cap, as will be discussed with reference toFIG. 5.

The one or more light sources 52 a, 52 b may be disposed on support arms54 a, 54 b. Light sources 52 a, 52 b may generate narrow light beams 53a, 53 b that may be directed towards the axis 45 a and intersect at apre-determined distance D from the lower surface 49 of the X-rayapplicator 30. Preferably, the distance D is selected to be between 0.5and 2 cm. The support arms 54 a, 54 b may be arranged so that lightbeams 53 a, 53 b do not intersect the X-ray applicator 30.

In use, a user may position the X-ray applicator 30 with respect to thepatient P in such a way that the beams 53 a, 53 b intersect at thesurface of the patient. However, should the treatment regime require theuse of a dose build-up material, the beams 53 a, 53 b may cross on asurface of the dose build-up material. In some embodiments, the supportarms 54 a, 54 b may be adjustable to indicate the central axis 45 a atdifferent distances from the lower surface 49 of the X-ray applicator30. In order to calibrate adjustment of the support arms, a transparentcalibration phantom may be used, wherein the central axis and depth aremarked.

It will be appreciated that although FIGS. 4 a-4 c disclose separateembodiments of the indicator, a combination of such embodiments iscontemplated as well. For example, embodiments directed to indicatingthe central axis may be combined with embodiments directed to indicatingthe complete field. In addition, internal and external indicators may becombined.

FIG. 5 presents a partial perspective view of the X-ray applicatorprovided with an applicator cap. The applicator cap 42 may bemanufactured from transparent glass, transparent plastic, or fromceramics as well as from PVDF and PPSU. Applicator cap 42 may also bemanufactured from a metal. In the latter case, the applicator cap may besterilized, otherwise, the applicator cap 42 may be a disposableapplicator cap 42. In view 50 of FIG. 4, it is seen that an outerdimension of the X-ray applicator 51 may be larger than the outerdimension of an exit portion covered by the applicator cap 42. Althoughsuch embodiment is preferable for minimizing total weight of the X-rayapplicator 51, it may be possible that the exit portion has the samedimension as the body of the X-ray applicator 51. In one embodiment, theapplicator cap may be 05-2 cm thick when manufactured from a lowZ-material.

FIGS. 6, 6E-E, and 6F-F, illustrate various views of the X-ray tube. TheX-ray tube 100 may have a body 102 enclosing at one end window 104through which the X-rays pass. See FIG. 8, cross-section E-E. The endwindow 104 may be made from a thin sheet of Beryllium metal. Anapplicator cap 106 may be positioned over the end window 104 so as tocovering the end window 104 and protect end window 104. Applicator cap106 may be made from a plastic material. The applicator cap may bemanufactured from PVDF (polyvinylidene fluoride) and has a thickness ofabout 0.4-0.7 mm, and preferably 0.6 mm, across the window portion.Alternatively, the applicator cap 106 may be manufactured from PPSU(polyphenylsulfone) and have a thickness of about 0.3-0.6 mm, andpreferably 0.5 mm, across the window portion.

In the tube body 102, a target 108 may be located at a range between 4and 10 cm from the collimator 130, and preferably between 4 and 5 cmfrom the collimator 130 (see FIG. 7, cross-section F-F). It will beappreciated that this distance is measured between the outer surface ofthe target 108 and a midplane of the collimator 130. The target 108 maybe made from Tungsten metal to provide the desired X-ray spectrum. Thetungsten tip of the target 108 may be mounted on a large anode assembly110 which also serves to dissipate the heat created from the generationof the X-rays in the target 108. Most of the anode assembly 110 is madefrom copper. The cathode 112 (see FIG. 7, cross-section F-F) may belocated slightly off-axis near the end window 104. Electrons emittedfrom the cathode are accelerated across the gap by the potentialdifference between the cathode and anode, in this case set at about 70kV, to the target 108 where the impact causes the generation of X-raysin a known manner. X-rays emitted from the target 108 pass through abeam hardening filter 122 before passing through a collimator 130 and anexit surface 124 on an applicator cap 106. The collimator 130 may behoused in a suitable collimator receptacle 128.

The anode assembly 110 may be mounted in the body 102 and electricallyinsulated. One of a number of known techniques and materials may be usedto provide the desired level of insulation between the anode assembly110 and the body 102.

As is well known in the art, the production of X-rays generates a largeamount of heat. Accordingly, it may be necessary to cool the X-ray tube100 in order to maintain it at a safe temperature. Various coolingmechanisms are known and used in the art. In one embodiment, the X-raytube 100 may be cooled by cooled water forced around the anode region.Cooled water enters the back of the tube by a first conduit 116 andleaves by a second conduit 118 (see FIG. 6, cross-section F-F). Thewater cooling circuit is a closed loop circuit, with the water leavingthe tube assembly 105 to be cooled by a remote cooler (not shown) beforereturning to the X-ray tube 100. It is contemplated that oil or anotherliquid may be used as the cooling medium. It is also known that apressurized gas may be used as an effective coolant in someapplications.

As is known in the art, X-rays are generated and emitted in alldirections, however the body 102 of the X-ray tube 100 and otherinternal components will tend to reduce the amount of radiation emittedfrom the body 102 of the X-ray tube 100 to a minimum, with most of theradiation emitted from the end window 104. The thickness of theshielding provided by the body 102 may be designed so that it providesat least the minimum level of shielding required for safe use by theoperator.

A high voltage cable assembly 120 may be connected to the anode assembly110. The high voltage cable assembly 120 may be connected to flexiblecable means (not shown) which in turn may be connected to a high voltagepower supply.

A radiation detector 114 may be placed outside the path of the X-raybeam emitted from the target 108 and passing through the end window 104.This detector can be any known form of radiation detector. In oneembodiment, the radiation detector may be a hardened semi-conductorconnected to an amplifier. The radiation detector 114 may detect whenthe tube 102 is working and emitting X-ray energy. Output from thedetector 114 may connected to a control unit, and the output signalsfrom the detector 114 may be used to provide an optical indication to auser of whether the tube is operating or not. By this means an X-raydetector 114 may be provided which may be used to detect if the X-raytube is on or off.

With further calibration of the radiation detector 114, it may bepossible to determine and calculate the X-ray dose administered to thepatient during the treatment. In this manner, it may be possible to havea real time dosimetry measurement system, in which the precise amount ofradiation dose administered can be determined. Once the dose rate isknown, a treatment plan can be modified during treatment. This may beadvantageous because it may enable a very accurate and carefullycontrolled dose of X-rays to be administered.

In order to enable the X-ray tube 100 to be placed accurately over atumour, a tumour illumination device may be is used. The tumourillumination device may include a plurality of lights 126 placed aroundthe circumference of the X-ray tube 100 near the end window 104. When inuse, the lights shine onto the skin of the patient. Since the lights 126are positioned around the circumference of the tube body 102, at a shortdistance from the end of the X-ray tube 100, they create a circle oflight with a sharp cut off of the inner part of the circle. In this way,the position of the lights on the tube body 102 may create a shadow.This shadow circle may be used to indicate the region which will besubject to irradiation when the X-ray tube 100 is turned on. It shouldbe appreciated the area within the circle may not be completely dark;the ambient light may be able to enter the shadow region.

In some embodiments, the lights 126 are white LEDs which can be brightenough to clearly illuminate the target region but do not generate largeamounts of heat and have very long lives. The lack of heat generation isimportant because the lights will be in close proximity to the skin ofthe patient, and so it is important to minimise the risk of burning orother damage to the skin. Other colours of LEDs may be used.Alternatively, other light sources could be used, such as known filamentlamps or even a remote light source connected to the ring by fiber opticcables.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A mobile X-ray unit comprising: a base for accommodating a controlunit for controlling an X-ray applicator and a power supply forsupplying power to an X-ray applicator; an articulated arm associatedwith the base and coupled to the X-ray applicator, wherein the X-rayapplicator has an X-ray tube for emitting an X-ray beam through an exitwindow to irradiate an object; and a dosimetry system adapted for realtime dosimetry of the emitted X-ray beam towards the object.
 2. Themobile X-ray unit according to claim 1, wherein the dosimetry system isprovided in the X-ray tube.
 3. The mobile X-ray unit according to claim1, wherein the dosimetry system is provided in the X-ray applicator. 4.The mobile X-ray unit according to claim 1, wherein the dosimetry systemis positioned between the exit window of the X-ray applicator and anobject being irradiated.
 5. The mobile X-ray unit according to claim 1,wherein the dosimetry system includes a semiconductor detector.
 6. Themobile X-ray unit according to claim 1, wherein the dosimetry system isconfigured to verify a position and geometry of an X-ray field.
 7. Themobile X-ray unit according to claim 1, wherein the dosimetry system iscalibrated to determine an absolute dosimetry of an X-ray dose.
 8. Themobile X-ray unit according to claim 1, further including at least onelight source configured to illuminate at least a portion of the X-raybeam emitted through the exit window of the X-ray applicator.
 9. Themobile X-ray unit according to claim 8, wherein the at least one lightsource includes two light sources concentrically arranged around one ofthe X-ray tube and the X-ray applicator.
 10. The mobile X-ray unitaccording to claim 9, wherein the X-ray beam has a longitudinal axis,and wherein each light source is arranged to emit a light beam towardsthe longitudinal axis at a pre-determined distance from a lower surfaceof the X-ray applicator.
 11. The mobile X-ray unit according to claim 8,wherein the light source is disposed inside the X-ray applicator forgenerating a light beam, wherein a collimator is configured to interceptthe light beam and provide a light image of the X-ray field emitted fromthe exit window.
 12. The mobile X-ray unit according to claim 8, furtherincluding an optical fiber configured to deliver light from the lightsource for interception by a collimator.
 13. The mobile X-ray unitaccording to claim 8, further including a plurality of optical fibersdistributed in the X-ray applicator in an area above the collimator forilluminating a collimator opening so as to provide a light image of theX-ray field.
 14. The mobile X-ray unit according to claim 8, wherein thelight source is configured to emit a light beam arranged inside theX-ray applicator to delineate a longitudinal axis of the X-ray beam. 15.The mobile X-ray unit according to claim 1, wherein the dosimetry systemis configured to generate a signal indicative of the X-ray beamgeneration.
 16. The mobile X-ray unit according claim 1, wherein dataobtained by the dosimetry system is corrected for a parameter selectedfrom a group consisting of: a temperature of the X-ray tube, an age ofthe X-ray tube, an angulation of the X-ray tube, and an energy of theX-ray beam.
 17. The mobile X-ray unit according to claim 1, wherein thedosimetry system is configured to deliver information about radiationdose distribution near a target region.
 18. A method for dosimetrycontrol of an X-ray beam emitted from a mobile X-ray unit, the mobileX-ray unit including a base for accommodating a control unit forcontrolling an X-ray applicator and a power supply for supplying powerto the X-ray applicator, an articulated arm associated with the base andcoupled to the X-ray applicator, wherein the X-ray applicator has anX-ray tube, the method comprising: controlling the X-ray applicator togenerate an X-ray beam; and measuring a radiation-related parameterassociated with the X-ray beam by using a dosimetry system.
 19. Themethod according to claim 21, further including delineating at least aportion of the X-ray beam.